A treatise on concrete, plain and reinforced : materials, construction, and design of concrete and reinforced concrete; 2nd ed. . mill is shown in Fig. 232. It consists essentially of a cylindrical drum,lined with castings of hard, tough steel, and containing forged steel balls8 or 10 inches in diameter. Rotation of the drum grinds the stone orclinker between the balls and the plates, and the powder passes throughsections of screens — which for clinker have usually 20 to 28 meshes tothe linear inch — into the hopper below. A single ball mill, such as isshown in sketch, running on clinker, shou
A treatise on concrete, plain and reinforced : materials, construction, and design of concrete and reinforced concrete; 2nd ed. . mill is shown in Fig. 232. It consists essentially of a cylindrical drum,lined with castings of hard, tough steel, and containing forged steel balls8 or 10 inches in diameter. Rotation of the drum grinds the stone orclinker between the balls and the plates, and the powder passes throughsections of screens — which for clinker have usually 20 to 28 meshes tothe linear inch — into the hopper below. A single ball mill, such as isshown in sketch, running on clinker, should give an output of, say, 5 500to 7 500 pounds per hour. A tube mill (see Fig. 233) consists of a long horizontal cylinder filled 7i6 A TREATISE ON CONCRETE nearly to its axle with flint pebbles imported from Europe, which averageabout 2 to 3 inches in diameter. The cement is ground by rolling aroundwith the flints. It is then thrown by centrifugal force against the screen,which regulates the fineness of grinding and prevents the passing of piecesof flint. A tube mill which passes, say, 250 barrels of cement per day,. Tube Mill. (See p. 71^.) will require the renewal of the flint pebl:)les at the rate of about 600 lb. per week. More tube mills than ball mills, usually twice as many, are required for the finish grinding. The Griffin mill (see Fig. 234) is used by many manufacturers in prefer-ence to ball and tube mills. Themill is driven by a horizontalpulley, from the center of which,by a universal joint, is suspendeda vertical shaft having fixed at itslower extremity a crushing roll,which revolves on its axis at aspeed of about 200 revolutionsper minute, and also rotates bycentrifugal force against the ringor die where the pulverizing isaccomphshed. The material tobe ground passes first into thepan below the crushing roll, uponthe under side of which are shoesor plows which stir it up and forceit up between the roll and the die.
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishernewyo, bookyear1912
